68. MINERAL ANALYSES FROM THE PERIDOTITE-GABBRO-BASALTCOMPLEX AT SITE 334, DSDP LEG 37
D.B. Clarke, Department of Geology, Dalhousie University, Halifax, Nova Scotia, Canadaand
H. Loubat, Département des Sciences de la Terre, Université de Quebec à Montreal, Montreal, P.Q.
ABSTRACT
Fifty-one analyses of silicates, oxides, and sulfides from a suite ofultrabasic and basic rocks at Site 334 are presented. The intrusiverocks show rhythmic, cryptic, and phase layering and are closelyanalogous to the Rhum-layered intrusion. The extrusive rocks aremineralogically similar to the intrusives, but are unlikely to begenetically related to them.
INTRODUCTION
Drilling at Site 334 penetrated ~50 meters of basaltswhich overlie at least 68 meters of gabbros andperidotites. The basalts are generally aphyric, or sparse-ly porphyritic containing phenocrysts of olivine, clino-pyroxene, and plagioclase. The presence of very coarsegrained rocks at shallow depth under the basalts is initself surprising and significant. The peridotites showwell-developed cumulus textures in which olivine andspinel are always cumulus phases, whereas two pyrox-enes and plagioclase are cumulus phases only in thegabbros. The present mineral analyses were under-taken to determine if the gabbros and peridotites arethe complements of the overlying basalts, i.e., if there isa genetic relationship between the intrusive rocks belowand the extrusive rocks above.
All analyses were done by electron microprobe(Cambridge Microscan MK-5) using natural mineralsas standards. The raw data were processed using theEMPADR VII correction procceedure of Rucklidgeand Gasparrini (1969).
MINERAL ANALYSESAnalyses of silicate minerals appear in Tables 1-3 and
are graphically represented in Figure 1. In addition,Table 4 contains analyses of chrome spinels from thethree peridotite specimens investigated. Also aqualitative petrographical investigation is summarizedin Table 5. Finally, some of thee rocks were brieflystudied for their sulfide mineralogy and the followingtwo analyses were made in gabbro 334-21-1, 47-49 cm:
Fe
Cu
Ni
S
Pyπte
47.83
-
0.07
53.27
Chalcopyrite
30.63
34.54
0.03
34.26
101.18 99.47
In other rocks, the following sulfides were identifiedbut not quantitatively analyzed: 22-2, 61-63 cm;
pentlandite; 23-1, 127-129 cm; pyrrhotite; 24-3, 112-114cm; chalcopyrite, pyrite, pentlandite. In many cases thesulfides appear to occur as disseminated blebs enclosedwithin the primary silicate minerals.
DISCUSSION
Within the limitations of the visual core descriptions(Aumento and Melson, 1974) and the low degree ofcore recovery, there appear to be at least nine cycles ofperidotite-olivine gabbro-gabbro in the plutonic com-plex of Site 334. A cycle usually begins with peridotite,but in some cases the most basic member may beolivine gabbro. Also, a cycle usually ends with olivine-poor or olivine-free gabbro, but in some cases the cycleends while the gabbro is still relatively olivine rich. Thiskind of rhythmic layering is found in several layeredbasic intrusions from the terrestrial environment(Wager and Brown, 1968). It remains to be seen whatthe nature of the cryptic layering is and whichterrestrial model most closely applies to the submarinesequence.
In Table 6 the samples are arranged in stratigraphicorder and the mineral chemistry is presented in sum-mary form. Samples 22-2, 61-63 cm and 21-1, 47-49 cmare from the same rhythmic unit, and it is apparent thatthere is normal cryptic variation from the peridotite tothe gabbro, i.e., increasing Fs molecule in the pyrox-enes. There is also elimination of olivine, presumablythrough a reaction relationship with the liquid at the 1atmosphere invariant point, 01 ~ + Opx+ + Cpx+ +Plag+ + Liquid". This reaction is strongly suggested bya careful petrographic examination: among the variousepisodes of crystallization, there is evidence of intensivereplacement, suggested by frequent lobate contactsbetween olivine relics, pyroxenes, and plagioclase. It isalso evident that whereas gabbro 21-1, 47-49 cm is theuppermost gabbro in the sequence, it is not the mostdifferentiated. The most evolved gabbro in terms of itsFs content in the pyroxenes is 23-1, 127-129 cm. A moreprimitive gabbro, 24-3, 112-114 cm, is found deeper inthe sequence.
The reversal in the Fs content of the pyroxenes (andAn content of the plagioclase) hints that the nine
847
D. B. CLARKE, H. LOUBAT
TABLE 1Microprobe Analyses of Olivines
Fo
FaLarn
Fo
Fa
Niol
F/MF/FM
1
88.50611.254
0.240
88.719
11.281
0.000
0.127
0.113
2
88.495
11.2790.227
88.696
11.304
0.000
0.127
0.113
3
83.15716.446
0.397
83.48916.511
0.000
0.198
0.165
4
88.637
10.884
0.479
89.063
10.937
0.000
0.123
0.109
5
85.283
14.2950.422
85.644
14.356
0.000
0.1680.144
6
85.746
13.9890.265
85.463
13.9430.594
0.163
0.140
7
87.51212.382
0.106
87.274
12.348
0.378
0.141
0.124
8
87.804
12.116
0.080
87.551
12.081
0.368
0.138
0.121
Note: 1 = 26-1, 20-22 cm; olivine 5. 2 = 26-1,20-22 cm;olivine 6. 3 = 15-2, 20 cm; olivine 1.4 = 15-2, 20cm;olivine 2. 5 = 20-2, 140-145 cm; olivine1.6 = 24-3, 112-114 cm; olivine 1.7 = 22-2,61-63 cm; olivine 1.8= 22-2, 61-63 cm; olivine 2.
LEGEND• Peridotite• Gabbro• Basalt•
Coexisting Phases
• HostLamell
Exsolved Pyroxenes
En
Fo
A n •
/ / /
w111Kff
20/ 30 40
% Fs ,Fa
50
,Ab
Fs
Fa
- A b
Figure 1. Mineral analyses forintrusive and extrusive rocksat Site 334.
rhythmic units are not the result of fractionalcrystallization of a single magma as is the case in theSkaergaard intrusion. Instead, the cyclical variation ofrock types and mineral chemistry suggests that thiscomplex has formed in a manner similar to thatdescribed for the Rhum-layered intrusion by Brown(1956). It is believed that these cumulates formed in amagma chamber that acted as a temporary reservoir formagmas en route to the surface. The longer the magmastayed in the reservoir, the more evolved would becomeboth the cumulate pile and the erupted basalt.
There is no compelling mineralogical evidence toprove or disprove a genetic link between the basalts andthe underlying intrusives. The basalts are more erraticin their mineral chemistry principally because mostphenocrysts in the basalts suggest that, if there is agenetic link, these basalts were erupted from themagma chamber at a stage of evolution between gab-bros of the types 24-3, 112-114 cm and 21-1, 47-49 cm.However, more convincing evidence exists against theidea that there is any genetic relationship between theintrusives and extrusives at Site 334. First, the closespatial relationship between the two groups makes un-likely the notion that the coarse-grained intrusivescould be in situ cumulates from the same magmas thatgave rise to the basalts. Secondly, the numerous brecciazones noted in the core logs, plus the cataclastic tex-
tures in the gabbros, suggest that these cumulates weretectonically emplaced. The greater the degree of dis-placement this type of deformation represents, the lesslikely it is that the intrusives and extrusives aregenetically related. Among the breccias, the mysteriousnannofossil chalk matrix could tentatively be explainedby a process of "oblique diapirism" of ultramafic lensesbeing serpentinized. The degree of serpentinization ofolivine is a direct function of the amount of olivine inthese rocks (i.e., a dunitic layer is totally serpentinized,and an olivine-poor gabbro has fresh olivine). If serpen-tinization occurred with an increase of volume, it couldresult in a dislocation of the layered sequence, across anoblique serpentinization front (Loubat, 1973). Lensesof brecciated serpentinites would eventually reach verysuperficial levels of the oceanic floor (Figure 2).
CONCLUSIONSThe conclusions listed below are tentative because of
the gaps in the core record and because of the limitedmineral data.
LEGEND
SEA LEVEL
Figure 2. Proposed shallow cross-section of the oceanicfloor at some distance away from the axis of a volcanicridge. Due to steeply oblique isotherms and serpentini-zation fronts, a lateral increase of volume and disloca-tion of ultramafic layers could occur. Some of thesebodies in the process of serpentinization will eventuallybe dragged in a phenomenon of "oblique diapirism,"and they could reach levels of superficial basalts andsediments, in a process of incipient dislocation of theoceanic floor. This could account for the differentialdegree of serpentinization of the layered body, the ob-vious increase of volume in the serpentinization, andthe breccias with chalky fossiliferous matrix.
848
MINERAL ANALYSES
SiO2
Tiθ2
A12O3
Cr 2 O 3
F e 2 O 3
FeOMnO
MgOCaO
Na2O
K2O
Sum
Si
AlAl
Ti
Cr
Fe3+
Fe
Mn
MgCa
Na
K
0
WO
EN
FS
WO
HYP
JD
F/MF/FM
SiO2
TiO2
Al 2 θ3
Cr 2 O 3
F e 2 O 3
FeO
MnO
MgO
CaO
Na2O
K2O
Sum
Si
Al
Al
Ti
Cr
Fe3+
Fe
Mn
Mg
Ca
NaK
0
1
53.69
0.201.19
0.07
0.00
18.85
0.23
25.09
0.65
0.07
0.02
99.98
1.966 *
0.034 2.000
0.014 *
0.006 *
0.002 *
0.000 *
0.578 *
0.007 *
1.369 1.975
0.026 *
0.005 *
0.001 0.031
6.000 *
1.293
69.426
29.281
1.28598.465
0.250
0.427
0.299
9
55.73
0.11
2.14
0.77
0.00
6.79
0.00
31.48
2.53
0.03
0.01
99.59
1.948 *
0.052 2.000
0.036 *
0.003 *
0.021 *
0.000 *
0.198 *
0.000 *
1.640 1.899
0.095 *
0.002 *
0.000 0.0976.000 *
2
53.32
0.32
1.75
0.09
0.00
7.63
0.25
14.85
22.23
0.26
0.04
100.74
1.961 *
0.039 2.000
0.037 *
0.009 *
0.003 *
0.000 *
0.235 *
0.008 *
0.814 1.105
0.876 *
0.019 *
0.002 0.8956.000 *
45.512
42.295
12.193
44.898
54.152
0.950
0.298
0.229
10
55.92
0.11
2.160.74
0.00
6.69
0.00
32.15
2.19
0.05
0.02
100.03
1.944 *
0.056 2.000
0.032 *
0.003 *
0.020 *
0.000 *0.194 *
0.000 *
1.666 1.915
0.082 *
0.003 *
0.001 0.0866.000 *
TABLE 2Micro probe Analyses of Pyroxenes
3
54.37
0.200.70
0.05
0.00
19.530.24
24.50
0.72
0.08
0.03
100.42
1.985 *
0.014 2.000
0.016 *
0.005 *
0.001 *
0.000 *
0.597 *
0.007 *
1.334 1.961
0.028 *
0.006 *
0.001 0.035
6.000 *
1.439
68.102
30.459
1.42998.284
0.287
0.453
0.312
11
50.55
0.22
3.691.27
0.00
3.64
0.11
18.52
19.56
0.15
0.06
97.77
1.880 *
0.120 2.000
0.042 *
0.006 *
0.037 *
0.000 *0.113 *
0.003 *
1.027 1.228
0.779 *
0.011 *
0.003 0.7936.000 *
4
52.36
0.401.55
0.09
0.00
8.500.22
14.97
21.53
0.26
0.05
99.93
1.950 *
0.050 2.000
0.018 *
0.011 *
0.003 *
0.000 *
0.265 *
0.007 *
0.831 1.134
0.859 *
0.019 *
0.002 0.880
6.000 *
43.947
42.510
13.543
43.377
55.675
0.948
0.327
0.246
12
51.200.24
3.17
1.27
0.00
3.36
0.10
17.99
20.75
0.20
0.07
98.35
1.896 *
0.104 2.000
0.034 *
0.007 *
0.037 *
0.000 *
0.014 *
0.003 *
0.993 1.178
0.823 *
0.014 *
0.003 0.841
6.000 *
5
52.61
0.302.24
0.14
0.00
7.07
0.2014.94
21.65
0.27
0.05
99.46
1.953 *
0.047 2.000
0.051 *
0.008 *
0.004 *
0.000 *
0.220 *
0.006 *
0.827 1.116
0.861 *
0.019 *
0.002 0.883
6.000 *
45.149
43.343
11.508
44.548
54.446
1.005
0.273
0.215
13
50.49
0.17
2.67
0.39
0.00
6.87
0.17
17.83
18.72
0.14
0.04
97.49
1.904 *
0.096 2.000
0.023 *
0.005 *
0.012 *
0.000 *
0.217 *
0.005 *
1.002 1.263
0.756 *
0.010 *
0.002 0.7696.000 *
6
42.33
0.41
1.84
0.08
0.008.54
0.23
14.38
21.62
0.26
0.06
99.75
1.952 *
0.048 2.000
0.033 *
0.012 *
0.002 *
0.000 *
0.266 *
0.007 *
0.800 1.120
0.864 *
0.019 *
0.003 0.886
6.000 *
44.771
41.426
13.804
44.174
54.865
0.961
0.431
0.255
14
50.68
0.25
2.24
0.24
0.007.96
0.20
16.98
18.27
0.14
0.05
97.01
1.926 *
0.074 2.000
0.027 *
0.007 *
0.007 *
0.000 *
0.253 *
0.006 *
0.962 1.262
0.744 *
0.010 *
0.002 0.757
6.000 *
7
53.47
0.211.14
0.06
0.00
20.29
0.29
23.35
1.10
0.09
0.03
100.03
1.973 *
0.027 2.000
0.022 *
0.006 *
0,002 *
0.000 *
0.626 *
0.009 *
1.284 1.949
0.043 *
0.006 *
0.001 0.051
6.000 *
2.226
65.729
32.046
2.20897.465
0.327
0.495
0.331
15
52.59
0.22
1.12
0.09
0.00
14.14
0.11
26.88
2.03
0.01
0.03
97.22
1.950 *
0.049 1.999
0.000 *
0.006 *
0.003 *
0.000 *
0.439 *
0.003 *
1.486 1.937
.0.081 *
0.001 *
0.001 0.083
6.000 *
8
53.51
0.37
2.97
1.330.00
2.72
0.00
16.35
21.98
0.90
0.03100.16
1.940 *
0.060 2.000
0.067 *
0.000 *
0.038 *
0.000 *
0.082 *
0.000 *
0.884 1.081
0.854 *
0.063 *
0.001 0.918
6.000 *
46.917
48.551
4.532
45.341
51.293
3.360
0.093
0.085
16
52.44
0.21
1.09
0.10
0.00
14.16
0.11
27.02
1.98
0.01
0.02
97.14
1.947 *
0.048 1.995
0.000 *
0.006 *
0.003 *
0.000 *
0.440 *
0.003 *
1.495 1.947
0.079 *
0.001 *
0.001 0.030
6.000 *
1) The sequence of nine rhythmic units in the in-trusive rocks at Site 334 appears to be the product of aRhum, rather than a Skaergaard, type of fractionalcrystallization.
2) Cryptic variation is present in the uppermost in-trusive unit, and it probably exists in each of the
rhythmic units. A detailed study of the phase chemistryof each rhythmic unit is suggested in order that the fullrecord of evolution may be understood.
3) There is phase layering in many of the units;olivine and chrome spinel are frequently observed atthe bottom, but not the top, of individual rhythmic
849
D. B. CLARKE, H. LOUBAT
TABLE 2 - Continued
10 12 13 14 16
WO
EN
FS
WO
EN
FS
4.901
84.833
10.266
4.200
85.784
10.016
40.510
53.491
5.899
42.872
51.709
5.419
38.293
50.738
10.969
37.979
49.105
12.916
4.023
74.105
21.872
3.911
74.255
21.834
WO
HYP
JO
F/M
F/FM
SiO2
Tiθ2
A12O3
C r 2 O 3
F e 2 O 3
FeO
MnO
MgO
CaO
Na 2O
K2O
Sum
Si
Al
Al
Ti
Cr
Fe3+
Fe
Mn
Mg
Ca
Na
K
O
4 896
94.999
0.105
0.121
0.108
17
52.24
0.43
3.70
0.00
0.00
5.80
0.15
17.88
19.90
0.18
0.06
100.34
1.902 *
0.098 2.000
0.060 *
0.012 *
0.000 *
0.000 *
0.177 *
0.005 *
0.970 1.223
0.776 *
0.013 *
0.003 0.792
6.000 *
4.193
95.634
0.173
0.117
0.105
18
51.12
0.00
5.58
0.00
0.00
6.48
0.00
18.40
17.85
0.14
0.00
99.57
1.868 *
0.132 2.000
0.108 *
0.000 *
0.000 *
0.000 *
0.198 *
0.000 *
1.002 1.308
0.699 *
0.010 *
0.000 0.709
6.000 *
40.310
59.131
0.559
0.114
0.102
19
52.14
0.00
3.81
0.00
0.00
6.60
0.00
20.88
14.71
0.13
0.00
98.27
1.913 *
0.087 2.000
0.078 *
0.000 *
0.000 *
0.000 *
0.202 *
0.000 *
1.142 1.422
0.578 *
0.009 *
0.000 0.587
6.000 *
42.48556.774
0.741
0.108
0.097
20
54.93
0.34
1.68
0.40
0.00
8.47
0.38
31.13
2.42
0.14
0.08
99.97
1.934 *
0.066 2.000
0.004 *
0.009 *
0.011 *
0.000 *
0.249 *
0.011 *
1.634 1.919
0.091 *
0.010 *
0.004 0.104
6.000 *
37.99161.495
0.514
0.222
0.181
21
55.20
0.33
1.80
0.40
0.00
8.33
0.37
30.80
2.46
0.15
0.08
99.92
1.942 *
0.058 2.000
0.016 *
0.019 *
0.011 *
0.000 *
0.245 *
0.011 *
1.615 1.907
0.093 *
0.010 *
0.004 0.107
6.000 *
37.65761.821
0.522
0.270
0.212
22
52.58
0.40
2.68
0.66
0.00
4.91
0.34
18.72
19.63
0.27
0.09
100.28
1.913 *
0.087 2.000
0.028 *
0.011 *
0.019 *
0.000 *
0.149 *
0.010 *
1.015 1.233
0.765 *
0.019 *
0.004 0.788
6.000 *
4.01595.950
0.036
0.297
0.229
23
52.90
0.41
2.55
0.57
0.00
4.29
0.34
17.35
20.27
0.27
0.09
99.04
1.943 *
0.057 2.000
0.053 *
0.011 *
0.017 *
0.010 *
0.132 *
0.011 *
0.960 1.173
2.798 *
0.019 *
0.004 0.321
6.000 *
3.90396.061
0.036
0.295
0.229
24
52.41
0.29
2.61
0.83
0.00
3.44
0.12
16.26
23.29
0.40
0.06
99.50
1.925 *
0.074 2.000
0.039 *
0.008 *
0.024 *
0.000 *
0.156 *
0.004 *
0.891 1.072
0.917 *
0.014 *
0.003 0.934
6.000 *
25
51.92
0.33
3.25
0.72
0.00
3.17
0.23
16.20
23.35
0.21
0.06
99.44
1.909 *
0.091 2.000
0.050 *
0.009 *
0.021 *
0.000 *
0.097 *
0.007 *
0.888 1.072
0.920 *
0.015 *
0.003 0.938
6.000 *
40.364
50.453
9.183
36.800
52.772
10.428
30.076
59.391
10.533
4.624
82.744
12.632
4.748
82.702
12.558
39.653
52.606
7.742
42.446
50.542
7.012
47.926
46.548
5.525
48.283
46.601
5.116
WOHYP
JD
F/M
F/FM
40.00459.342
0.655
0.187
0.157
36.60962.871
0.520
0.198
0.165
29.93269.589
0.479
0.177
0.151
4.57594.946
0.479
0.160
0.138
4.69794.785
0.518
0.159
0.137
39.05559.973
0.972
0.157
0.136
41.78357.210
1.007
0.150
0.130
47.48051.732
0.733
0.123
0.109
47.72851.495
0.777
0.118
0.105
Note: 1 = 23-1, 127-129 cm; OPX host 1. 2 = 23-1, 127-129 cm; CPX lamella 1A. 3 =23-1, 127-129 cm; OPX host 2.4 = 23-1, 127-129 cm; CPX lamella 2A. 5 = 23-1,127-129 cm; CPX host 3. 6 = 23-1, 127-129 cm; CPX host 4. 7 = 23-1, 127-129 cm; OPX lamella 4A. 8 = 26-1, 20-22 cm; OPX 3. 9 = 26-1, 20-22 cm; OPX 7.10=26-1,20-22 cm;OPX 8. 11 = 26-1, 20-22 cm; CPX 9. 12 = 26-1, 20-22 cm; CPX 10. 13 = 21-1,4749 cm; CPX 1. 14 = 21-1,4749 cm; CPX 2.15 = 21-1,4749 cm; OPX 3.16 = 21-1, 4749 cm; OPX 4. 17 = 15-2, 30 cm; CPX 1. 18 = 20-2, 140-145 cm; CPX 3. 19 = 20-2,140-145 cm; CPX 4. 20 = 24-3, 112-144 cm; OPX 2. 21 =24-3, 112-114 cm; OPX 3. 22 = 24-3, 112-114 cm; CPX 4. 23 = 24-3, 112-114 cm; CPX 5. 24 = 22-2, 61-63 cm; CPX 3. 25 = 22-2, 61-63 cm; CPX 4.
units. This phase layering is attributed to reactionrelationships in a fractionating magma rather thansettling of dense crystals in rhythmic units developed by"turbidity currents" in the magma chamber.
4) The mineral chemistry alone is not sufficient to es-tablish or disprove a genetic link between the basaltsand the underlying intrusives.
5) A genetic link between intrusives and extrusives isunlikely because of the close spatial association of therocks and because of the deformation of the intrusivessuggesting that they have been tectonically emplaced.
REFERENCESAumento, F. and Melson, W.G., 1974. DSDP Leg 37 visual
core descriptions and sample distribution for igneous
cores, Holes 332A, 332B, 333A, 334, 335: DSDP Leg 37Shipboard Report.
Brown, G.M., 1956. The layered ultrabasic rocks of Rhum,inner Hebrides: Phil. Trans. Roy. Soc. London, Series240B, p. 1-53.
LoubaL, H., 1973. Soubassement des dorsales volcaniquesocéaniques: Suisse Min. Petrol. Bull., v. 53, p. 337-354.
Rucklidge, J. and Gasparrini, E.L., 1969. Electronmicroprobe analytical data reduction: Dept. of Geology,Institute of Toronto, Canada.
Wager, L.R. and Brown, G.M., 1968. Layered igneous rocks:Edinburgh (Oliver and Boyd).
850
TABLE 3Microprobe Analyses of Feldspars
oo
Siθ2Tiθ2AI2O3Cr 2O 3
Fe 2 O 3
FeO
MnO
MgO
CaO
Na2θK 2 O
Sum
Si
Ti
Al
Fe3+Fe
Mn
Mg
Ca
Na
K
0
Or
AB
AN
QZ
NE
KS
Note: 1
1
48.190.05
32.130.000.000.000.000.00
16.612.230.07
99.28
8.900 *0.887 *6.992 *0.000 *0.000 *0.000 *0.000 15.8993.287 *0.798 *0.016 4.102
32.000 *
0.40219.46880.130
91.6118.2190.178
= 23-1, 127-129 cm;ioclase 8. 7 = 15-2, 20 cm;
2
47.300.05
32.460.000.000.000.000.00
15.742.150.06
99.22
8.8370.3177.0720.0000.0000.000
3
47.570.04
32.650.00
0.000.000.000.00
16.981.970.07
99.28
* 8.795 ** 0.006 ** 7.113 ** 0.000 ** 0.000 ** 0.000 *
0.000 15.916 0.000 15.9143.3080.7710.014 4
32.000
0.34618.83080.825
91.8448.0000.147
plagioclase 5.plagioclase 1.!
* 3.364 ** 0.786 *.093 0.017 4.086* 32.000 *
0.48417.28282.314
92.4077.4200.173
4
47.000.04
32.930.000.000.000.000.00
17.551.660.06
99.24
8.787 *0.006 *7.188 *0.000 *0.000 *0.000 *0.000 15.9013.483 *0.596 *0.014 4.094
32.000 *
0.34614.56484.090
93.4496.3990.152
2 = 23-1, 127-129 cm; plagioclase 6. 3 = 21-1
5
46.870.05
32.730.000.000.000.000.00
17.591.660.06
98.96
8.711 *0.007 *7.168 *0.000 *0.000 *0.000 *0.000 15.8663.603 *0.598 *0.014 4.115
32.000 *
0.34614.53685.118
93.4326.4160.153
6
48.300.05
32.11
0.000.000.000.000.00
16.592.140.07
99.26
8.916 *0.007 *6.985 *0.000 *0.000 *0.000 *0.000 15.9083.281 *0.766 *0.016 4.064
32.000 *
0.40618.84380.746
91.9337.8970.170
7
46.470.00
33.680.000.000.290.000.33
18.251.120.00
100.14
8.553 *0.000 *7.304 *0.000 *0.045 *0.000 *0.091 15.9923.599 *0.400 *0.000 3.998
32.000 *
0.0009.995
90.005
95.5364.4640.000
, 47-49 cm; plagioclase 5.4 = 21-1,47-49 cm; plagioclase 6.55 = 20-2,140-145 cm; plagioclase 1.9 = 20-2, 140-145 cm; plagioclase 2. 10= 24-3,112-114 cm; plagioclase 6
8
51.330.00
29.390.000.000.750.000.58
14.852.610.00
99.52
9.409 *0.000 *6.348 *0.000 *0.117 *0.000 *0.158 16.0332.917 *0.928 *0.000 3.844
32.000 *
0.00024.13075.870
91.0268.9740.000
= 21-1,4749 cm;
9
50.41
0.0029.98
0.000.000.740.000.51
15.402.600.00
99.64
9.259 *0.000 *6.488 *0.000 *0.114 *0.000 *0.140 16.0003.030 *0.926 *0.000 3.956
32.000 *
0.00023.40276.598
90.9099.0910.000
plagioclase 7. 6 = 21-1
10
45.720.02
33.390.000.000.000.000.00
18.171.320.05
98.67
8.541 *0.003 *7.391 *0.000 *0.000 *0.000 *0.000 15.8953.637 *0.478 *0.312 4.127
32.000 *
0.28311.58588.126
94.5745.2940.132
,47-49 cm;ρlag- MIN
ER
AL
AN
AL
YS
E
D. B. CLARKE, H. LOUBAT
TABLE 4Microprobe Analyses of Spinels
SiO2
TiO2
AI2O3Fe2O3
FeOCr2O3
MnOMgOZnOCaOSum
SiTiAlCr
Fe3+FeMn
MgZn
Ca0
CHROSPINMAGN
USP
SPINMAGN
USP
CHROMAGN
F/M
F/FM
1
0.00
0.3724.66
2.7715.5243.12
0.29
13.390.000.02
100.14
0.000 *
0.068 *7.064 *
8.288 *0.507 15.9263.155 *0.060 *4.852 *0.000 *0.005 8.072
32.000 *
52.26044.545
3.195
0.88692.481
6.634
0.76393.519
5.718
0.6630.399
2
0.000.40
22.103.93
18.6843.33
0.3710.94
0.000.02
99.77
0.000 *0.075 *6.522 *
8.580 *0.741 15.9183.913 *0.078 *4.084 *0.000 *0.005 8.080
32.000 *
54.15641.1694.675
1.027
88.88010.903
0.08291.315
7.883
0.9770.494
3
0.000.66
21.584.73
17.5142.86
0.3611.730.000.02
99.45
0.000 *0.124 *
6.369 *8.486 *0.891 15.8713.667 *0.076 *4.379 *0.000 *0.005 8.128
32.000 *
53.89540.444
5.661
1.68386.24512.072
1.30889.311
9.381
0.8550.461
4
0.00
0.7021.594.62
17.8343.50
0.3611.740.000.02
100.36
0.000 *0.131 *6.322 *
8.547 *0.864 15.864
3.705 *0.076 *4.348 *0.000 *0.005 8.135
32.000 *
54.324
40.185
5.491
1.78886.40511.807
1.37189.5749.055
0.8700.465
5
0.010.63
21.645.05
19.2642.41
0.37
10.610.000.01
99.89
0.003 *
0.100 *6.409 *8.427 *0.955 15.894
4.048 *0.079 *3.975 *0.000 *0.003 8.104
32.000 *
53.36640.585
6.048
1.34285.86212.796
1.05688.87110.072
1.0380.509
6
0.020.52
20.655.16
20.62
42.910.41
9.600.000.02
99.91
0.005 *0.099 *6.181 *
8.618 *0.986 15.8904.380 *0.088 *3.635 *0.000 *0.005 8.109
32.000 *
54.594
39.158
6.248
1.367
85.06013.573
1.02488.81210.165
1.2290.551
Note: 1 = 26-1, 20-22 cm; spinel 1.2 = 26-1, 20-22 cm; spinel 2.3 = 26-2, 5-10 cm; spinel 1.4 = 26-2, 5-10 cm; spinel 2. 5 = 22-2,61-63 cm; spinel 6.6 = 22-2, 61 63 cm; spinel 7.
852
MINERAL ANALYSES
TABLE 5Summary of Petrography
Sample(Interval in cm)
15-2, 20
20-2, 140-145
21-1,47-49
22-1, 17-23
22-2,61-63
22-2, 80-82
23-1,46-54
23-1,91-93
23-1,127-129
23-2, 78-82
24-2,105-107
24-3,112-114
24-4,100-106
26-1,20-22
Rock Type
Basalt
Basalt
Anorthositicgabbro
Gabbro
Peridotite
Perdotite
Peridotite
Gabbro
Noriticgabbro
Peridotite
Olivinegabbro
Olivineleucogabbro
Olivinegabbro
Peridotite
Modal Analysis
PlagioclaseClinopyroxeneOlivine
PlagioclaseClinopyroxeneQuench crystalsOlivine
PlagioclaseClinopyroxene
PlagioclasePyroxene
OlivineClinopyroxeneRodingite
OlivineClinopyroxeneOrthopyroxeneChromite
OlivineIddingsiteOpxCpxPlag
PlagioclaseClinopyroxene
PlagioclasePyroxenes
OlivineOrthopyroxenePlagioclaseChromite
OlivinePlagioclaseClinopyroxene
OlivinePlagioclasePyroxenes
OlivinePlagioclasePyroxenes
OlivinePyroxenesRodingiteSpinels
5045
5
55
90Tr
6040
6040
701515
601822Tr
AΠou
40
5050
4060
701515Tr
155035
55540
352045
6030
55
Grain Size (mm)
Phenocrysts <3Groundmass <l
< l
1-6
Phenocrysts <3
Olivine 10-20Cpx 14mm
Olivine 1-2Cpx 8-15
Olivine 10-12
<2
3-15
<2
Generally <4
1-6
Olivine <IOPlag<2Pyroxene 4
3-10
Texture
Porphyritic(phenocrysts ofPlag, Cpx, Oliv)
Microporphyriticrock consistingmainly of quenchcrystals in vario-litic texture
Plagioclase-Cpxadcumulate; ex-solution in Cpx
Cumulus plagio-clase; intercumuluspyroxene
Cumulus olivine;intercumulus Cpxwith minor ex-solution
Cpx exsolved;olivine cumuluspyroxenes inter-cumulus; mesh
Olivines corroded;exsolution lamellaein fresh Cpx
Ophitic;minor cataclasis;plagioclase cumutlus; clirropyroxèneintercumulusAdcumulate;augite and invertedpigeonite bothwith exsolutionlamellae; cata-clastizedTrace of exso-lution in alteredOpx
Plag poikiliticin Cpx
Adcumulate
Opx and Cpxzoned, exsolvedand with kinkbands; olivine andplagioclase cumulus
Cumulus olivineand spinel; inter-cumulus plagio-clase mesh; bastite;pyroxenes withexsolution
Alteration
Minor chloritein vesicles
Fresh
Minor sericite
Partially amphi-bolitized
Olivine 95%serpentinized
Olivine and ortho-pyroxene partlyserpentinized
Olivine totallyserpentinized,Opx-Cpx-Plagserpentinizedand rodingitized
Fresh
Fresh
Olivine and ortho-pyroxene totallyserpentinized;plagioclaserodingitized
Olivine partly alter-ed to serpentineand iddingsiteOlivine partlyserpentinized
Olivine partlyserpentinized
Olivine altered toserpentine
853
D. B. CLARKE, H. LOUBAT
TABLE 5 - Continued
Sample(Interval in cm)
26-1, 70-75
26-2, 5-10
26-2, 56-71
26-2, 59-64
Rock Type
Peridotite
Peridotite
Olivinegabbro
Olivinegabbro(Pyroxenite)
Modal Analysis
OlivineClinopyroxeneOrthopyroxeneChromiteOlivinePyroxenesRodingiteSpinel
OlivinePlagioclasePyroxenes
OlivinePlagioclasePyroxenes
652213Tr
8015
J
204040
102070
Grain Size (mm)
Generally <IO
2-3
<4
<3
Texture
Cpx with exsolu-tion lamellae;Olivine cumulus;Cpx intercumulusCumulus olivineand spinel;intercumuluspyroxenes andplagioclase; mesh;bastiteExsolution lamel-lae in pyroxenes;cumulus plagioclase(and olivine?)Plagioclase cumu-lus; pyroxenes withexsolutionlamellae
Alteration
Olivine totallyserpentinized;Opx partlyserpentinizedOlivine totallyserpentinized;Opx partlyserpentinized
Olivine partlyserpentinized
Olivineserpentinized
854
MINERAL ANALYSES
TABLE 6Summary of Mineral Chemistry for Intrusive Rocks at Site 334
Depth(m) Cycle Rock Type
Sample(Interval in cm) Phase Chemistry
310-
-315 -
----
3 2 0 ---_*_*
3 2 5 --_*-_*
330--
-
_*
335-
_
-__*
340-*_*_*
__*
345---_*-
350-*----
3 3 5 -----
3 6 0 -
_*_*
-
365-*--_-
370-
GGGGGGGGGGGPPPGGGPGPG
P
GpGGGGGOGOGOGOGOGOGOGOGOGPPPPGGGGGGGG
PPPPOGOGGGGOG
21-1,4749
22-1, 17-23
22-2,61-6322-2, 80-8223-1,46-5423-1,91-9323-1, 127-129
23-2, 78-82
24-2, 105-107
24-3,112-114
244, 100-106
26-1, 20-22
26-1, 70-7526-2, 5-1026-2,56-7126-2, 59-64
Olivine absentWO38EΠ5QFSJ2
\V04En74Fs22An80-85
\V048En47Fs5Cr54Sp4()Mt6
Olivine absent
\V042En67Fs31
Anso
F o 8 5
" ° 1 51 8\V05En83Fs12A n 8 8
Fo 8 8\V042En53Fs5
\V04En85Fsn
Cr54Sp4θMt5
Cr53Sp43Mt4
Gabbro
Peridotite
Gabbro
Gabbro
Peridotite
Peridotite
Note: P = Peridotite; OG = Olivine Gabbro; G = Gabbro; * = Breccia.
855
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